From mboxrd@z Thu Jan 1 00:00:00 1970 From: Douglas Gilbert Subject: Re: [PATCH v5 0/4] [SCSI] sg: fix race condition in sg_open Date: Sat, 03 Aug 2013 01:25:29 -0400 Message-ID: <51FC9449.4060906@interlog.com> References: <1374075246-22923-1-git-send-email-vaughan.cao@oracle.com> <1374468033-8947-1-git-send-email-vaughan.cao@oracle.com> <20130722170338.GA15824@logfs.org> <51F9EB97.7070305@interlog.com> Reply-To: dgilbert@interlog.com Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: <51F9EB97.7070305@interlog.com> Sender: linux-kernel-owner@vger.kernel.org To: =?UTF-8?B?SsO2cm4gRW5nZWw=?= , Vaughan Cao Cc: JBottomley@parallels.com, linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org List-Id: linux-scsi@vger.kernel.org On 13-08-01 01:01 AM, Douglas Gilbert wrote: > On 13-07-22 01:03 PM, J=C3=B6rn Engel wrote: >> On Mon, 22 July 2013 12:40:29 +0800, Vaughan Cao wrote: >>> >>> There is a race when open sg with O_EXCL flag. Also a race may happ= en between >>> sg_open and sg_remove. >>> >>> Changes from v4: >>> * [3/4] use ERR_PTR series instead of adding another parameter in= sg_add_sfp >>> * [4/4] fix conflict for cherry-pick from v3. >>> >>> Changes from v3: >>> * release o_sem in sg_release(), not in sg_remove_sfp(). >>> * not set exclude with sfd_lock held. >>> >>> Vaughan Cao (4): >>> [SCSI] sg: use rwsem to solve race during exclusive open >>> [SCSI] sg: no need sg_open_exclusive_lock >>> [SCSI] sg: checking sdp->detached isn't protected when open >>> [SCSI] sg: push file descriptor list locking down to per-device >>> locking >>> >>> drivers/scsi/sg.c | 178 +++++++++++++++++++++++++----------------= ------------- >>> 1 file changed, 83 insertions(+), 95 deletions(-) >> >> Patchset looks good to me, although I didn't test it on hardware yet= =2E >> Signed-off-by: Joern Engel >> >> James, care to pick this up? > > Acked-by: Douglas Gilbert > > Tested O_EXCL with multiple processes and threads; passed. > sg driver prior to this patch had "leaky" O_EXCL logic > according to the same test. Block device passed. > > James, could you clean this up: > drivers/scsi/sg.c:242:6: warning: unused variable =E2=80=98res=E2=80= =99 [-Wunused-variable] =46urther testing suggests this patch on the sg driver is broken, so I'll rescind my ack. The case it is broken for is when a device is opened without O_EXCL. Now if, while it is open, a second thread/process tries to open the same device O_EXCL then IMO the second open should fail with EBUSY. My testing shows that O_EXCL opens properly deflect other O_EXCL opens. BTW the standard block driver (e.g. /dev/sdc) is broken in exactly the same way, according to my tests. Doug Gilbert